The present invention relates to a plate-making method and a plate-making apparatus, which perform digital plate-making by an electrostatic ink jet process using an oil-based ink, and also relates to a computer-to-cylinder type lithographic printing method and a computer-to-cylinder type lithographic printing apparatus, which perform the above-described digital plate-making on the printing apparatus and subsequently performing printing. More specifically, the present invention relates to a plate-making method, a plate-making apparatus, a computer-to-cylinder type lithographic printing method and a computer-to-cylinder type lithographic printing apparatus, where the oil is filtered before use and thereby, the image on the printing plate and the printed image are improved in the quality.
In the lithographic printing, the printing is performed by forming an ink-receptive region and an ink-repulsive region on the surface of a printing plate in correspondence to an image original and adhering a printing ink to the ink-receptive region. Usually, hydrophilic and lipophilic (ink-receptive) regions are imagewise formed on the surface of a printing plate and the hydrophilic region is rendered ink-repulsive using a fountain solution.
In general, the formation of an image (plate-making) on a printing original plate (plate material) is heretofore performed by a method of once outputting an image original on a silver salt photographic film in an analog or digital manner, exposing a diazo resin or photopolymerizable photopolymer light-sensitive material (plate material) through the film and then, dissolving and removing the non-image area using an alkaline developer.
In recent years, the lithographic printing method is demanded to meet requirements for more improvement in the digital drawing technique and higher efficiency in the process thereof and in view of these recent requirements, a large number of systems for directly recording digital image information have been proposed. These techniques are called CTP (computer-to-plate) or DDPP (digital direct printing plate), With respect to the plate-making method, for example, a system of recording an image in the light or heat mode using a laser has been proposed and this system is partially put into practical use.
However, even in this plate-making method, irrespective of light mode or heat mode, the plate-making generally involves a treatment with an alkaline developer after the laser recording to dissolve and remove the non-image area, therefore, an alkaline waste solution is discharged and this is not preferred in view of the environmental conservation.
In the method of using a laser, an expensive and large-scale apparatus is necessary. In this respect, a system applying an ink jet process which is an inexpensive and compact recording device, has been proposed.
JP-A-64-27953 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a method of forming an image on a hydrophilic plate material by an ink jet process using a lipophilic wax ink, thereby performing plate-making. In this method, the image is formed by a wax and therefore, the image area is weak in the mechanical strength and deficient in the adhesive property to the hydrophilic surface of the plate material, which gives rise to poor press life.
As means for realizing an efficient printing process, a system of performing the image formation on a printing apparatus is known. JP-A-4-97848 discloses a method of providing a plate drum having a hydrophilic or lipophilic surface area in place of a conventional plate cylinder, forming thereon a lipophilic or hydrophilic image by an ink jet process, and removing and cleaning the image after the completion of printing. In this method, however, it is difficult to attain easy removing (namely, cleaning) of the printed image and a sufficiently long press life at the same time. Furthermore, in the case of forming an image having high press life on the plate drum, an ink containing a resin in a relatively high concentration must be used and accompanying the evaporation of solvent at the nozzle part, the resin readily fixes to the ink jet means of forming a printing image, as a result, the ink ejection stability decreases and a good image cannot be obtained.
In the case of forming an image by an ink jet process, aggregates in the ink or foreign matters such as dust fed to the ejection head cause clogging of the head and this gives rise to unstable ejection of ink and in turn deterioration in the image quality or stopping of the ejection. The present invention has been made to overcome these problems.
An object of the present invention is to provide a plate-making method for manufacturing a lithographic printing plate which ensures printing of a large number of printed matters having a clear and high-quality image by an inexpensive and simple process, where a development processing is not necessary and a digital technique can be adopted.
Another object of the present invention is to provide a plate-making apparatus for realizing this plate-making method.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing method capable of blocking flowing of aggregates or foreign matters such as dust and always feeding an ink kept in a normal state to an ejection head, where a development processing is not necessary and a digital technique can be adopted.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing apparatus for realizing this computer-to-cylinder type lithographic printing method.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing method capable of printing a large number of printed matters having a clear and high-quality image by an inexpensive apparatus and a simple and easy method.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing apparatus for realizing this computer-to-cylinder type lithographic printing method.
Other objects and effects of the present invention will become apparent from the following description.
The above-described objects of the present invention have been achieved by providing the following methods and apparatuses.
1) A plate-making method comprising:
filtering an oil-based ink;
forming an image directly on a plate material by an ink jet process comprising ejecting said filtered oil-based ink using electrostatic field based on signals of image data; and
fixing said formed image to prepare a printing plate.
2) The plate-making method according to item 1) above, wherein said oil-based comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
a component dispersed in the nonaqueous solvent, comprising at least resin particles which are solid and are hydrophobic at least at ordinary temperatures.
3) A plate-making apparatus comprising:
an image-forming unit which forms an image directly on a plate material based on signals of image data; and
an image-fixing unit which fixes the image formed by said image-forming unit to prepare a printing plate,
wherein said image-forming unit comprises an ink jet drawing device having an ejection head which ejects an oil-based ink using electrostatic field and having at least one ink-filtering member provided in a passage of said oil-based ink.
4) The plate-making apparatus according to item 3) above, wherein said filtering member is provided at a portion immediately preceding an ink ejection part of said ejection head.
5) The plate-making apparatus according to item 3) or 4) above, wherein said filtering member comprises a filter material which blocks coarse aggregates of said oil-based ink and foreign matters including dust mingled during the image formation.
6) The plate-making apparatus according to item 5) above, wherein said filter material has pores having various shapes and sizes, each of said pores having a minimum distance of not less than 2 xcexcm.
7) The plate-making apparatus according to item 5) or 6) above, wherein said filter material has a single-layer or multilayer structure.
8) The plate-making apparatus according to item 7) above, wherein said multilayer filter material comprises filter material layers including; a coarsest protective body and a coarsest support provided in an upstream side and a downstream side, respectively; and intervening filter material layers provided between said protective body and support in such a manner that the pore sizes of said intervening filter materials are sequentially reduced toward the downstream side.
9) The plate-making apparatus according to any one of items 5) to 8) above, wherein said filter material has at least one figuration selected from the group consisting of a single plate form, a tea strainer form, a coming back form and a cylinder form.
10) The plate-making apparatus according to any one of items 5) to 9) above, wherein said filter material comprises at least one material selected from the group consisting of paper, plastic, metal, ceramic and glass.
11) The plate-making apparatus according to any one of items 5) to 10) above, wherein said filter material is of cartridge-type and exchangeable.
12) The plate-making apparatus according to any one of items 5) to 11) above, further comprising a filter material accumulation-removing member which removes substances accumulated on said filter material.
13) The plate-making apparatus according to item 12) above, wherein said removal of the filter material accumulation is performed by at least one of ultrasonic irradiation, vibration, and back flow of said ink or a cleaning solution.
14) The plate-making apparatus according to item 3) or 4) above, wherein said filtering member comprises at least one filtering system selected from the group consisting of gravity filtration, pressure filtration, vacuum filtration and constant rate filtration.
15) The plate-making apparatus according to any one of items 3) to 14) above, wherein said oil-based ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
a component dispersed in the nonaqueous solvent, comprising at least resin particles which are solid and are hydrophobic at least at ordinary temperatures.
16) The plate-making apparatus according to any one of items 3) to 15) above, wherein said image-fixing unit has a heating member comprising at least one of a heat roller, an infrared lamp, a halogen lamp and a xenon lamp.
17) The plate-making apparatus according to item 16) above, wherein said heating member is disposed and/or controlled to gradually elevate a temperature of said plate material at the time of said fixing.
18) The plate-making apparatus according to any one of items 3) to 17) above, further comprising a drum for mounting said plate material thereon, said drum being rotatable to perform main scanning upon said image formation.
19) The plate-making apparatus according to item 18) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction parallel to the axis of said drum to perform sub-scanning upon said image formation.
20) The plate-making apparatus according to any one of items 3) to 17) above, further comprising at least a pair of capstan rollers for running said plate material while being interposed and held therebetween to perform sub-scanning upon said image formation.
21) The plate-making apparatus according to item 20) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction orthogonal to the running direction of said plate material to perform main scanning upon said image formation.
22) The plate-making apparatus according to item 18) or 20) above, wherein said ejection head comprises a full line head having almost the same length as the width of said plate material.
23) The plate-making apparatus according to any one of items 3) to 22) above, wherein said ink jet drawing device has an ink feed member which feeds said oil-based ink to said ejection head.
24) The plate-making apparatus according to item 23) above, which comprises an ink recovery member which recovers said oil-based ink from said ejection head to circulate said ink.
25) The plate-making apparatus according to any one of items 3) to 24) above, which comprises a dust-removing member which removes dusts present on the surface of said plate material at least one of before and during said image formation.
26) The plate-making apparatus according to any one of items 3) to 25) above, wherein said ink jet drawing device has an ink tank for storing said oil-based ink and a stirring member which stirs the oil-based ink in said ink tank.
27) The plate-making apparatus according to any one of items 3) to 26) above, wherein said ink jet drawing device has an ink tank for storing said oil-based ink and an ink temperature-controlling member which controls the temperature of the oil-based ink in said ink tank.
28) The plate-making apparatus according to any one of items 3) to 27) above, wherein said ink jet drawing device has an ink concentration-controlling member which controls the concentration of said oil-based ink.
29) The plate-making apparatus according to any one of items 3) to 28) above, which comprises an ejection head-cleaning member.
30) A computer-to-cylinder type lithographic printing method comprising:
mounting a plate material onto a plate cylinder of a printing apparatus;
filtering an oil-based ink;
forming an image directly on said plate material by an ink jet process comprising ejecting said filtered oil-based ink from an ejection head using electrostatic field based on signals of image data;
fixing said image to prepare a printing plate; and
performing lithographic printing with said printing plate.
31) The computer-to-cylinder type lithographic printing process according to item 30) above, wherein said oil-based ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
a component dispersed in the nonaqueous solvent, comprising at least resin particles which are solid and are hydrophobic at least at ordinary temperatures.
32) A computer-to-cylinder type lithographic printing apparatus comprising:
a plate cylinder;
an image-forming unit which directly forms an image on a plate material mounted onto said plate cylinder based on signals of image data;
an image-fixing unit which fixes the image formed by said image-forming unit to prepare a printing plate; and
a lithographic printing unit which performs lithographic printing with the printing plate,
wherein said image-forming unit comprises an ink jet drawing device having an ejection head which ejects an oil-based ink using electrostatic field and having at least one ink filtering member provided in a passage of said oil-based ink.
33) The computer-to-cylinder type lithographic printing apparatus according to item 32) above, wherein said filtering member is provided at a portion immediately preceding an ink ejection part of said ejection head.
34) The computer-to-cylinder type lithographic printing apparatus according to item 32) or 33) above, wherein said filtering member comprising a filter material which blocks coarse aggregates of said ink and foreign matters including dust mingled during the image formation.
35) The computer-to-cylinder type lithographic printing apparatus according to item 34) above, wherein said filter material has pores having various shapes and sizes, each of said pores having a minimum distance of not less than 2 xcexcm.
36) The computer-to-cylinder type lithographic printing apparatus according to item 34) or 35) above, wherein said filter material has a single-layer or multilayer structure.
37) The computer-to-cylinder type lithographic printing apparatus according to item 36) above, wherein said multilayer filter material comprises filter material layers including: a coarsest protective body and a coarsest support provided in an upstream side and a downstream side, respectively; and intervening filter material layers provided between said protective body and support in such a manner that the pore sizes of said intervening filter materials are sequentially reduced toward the downstream side.
38) The computer-to-cylinder type lithographic printing apparatus according to any one of items 34) to 37) above, wherein said filter material has at least one figuration selected from the group consisting of a single plate form, a tea strainer form, a coming back form and a cylinder form.
39) The computer-to-cylinder type lithographic printing apparatus according to any one of items 34) to 38) above, wherein said filter material comprises at least one material selected from the group consisting of paper, plastic, metal, ceramic and glass.
40) The computer-to-cylinder type lithographic printing apparatus according to any one of items 34) to 39) above, wherein said filter material is of cartridge-type and exchangeable.
41) The computer-to-cylinder type lithographic printing apparatus according to any one of items 34) to 40) above, further comprising a filter material accumulation-removing member which removes substances accumulated on said filter material.
42) The computer-to-cylinder type lithographic printing apparatus according to item 41) above, wherein said removal of the filter material accumulation is performed by at least one of ultrasonic irradiation, vibration, and back flow of said ink or a cleaning solution
43) The computer-to-cylinder type lithographic printing apparatus according to item 32) or 33) above, wherein said filtering member comprises at least one filtering system selected from the group consisting of gravity filtration, pressure filtration, vacuum filtration and constant rate filtration.
44) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 43) above, wherein said oil-based ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
a component dispersed in the nonaqueous solvent, comprising at least resin particles which are solid and are hydrophobic at least at ordinary temperatures.
45) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 44) above, wherein said image-forming unit comprises a dust-removing member which removes dusts present on the surface of the plate material at least one of before and during said image formation.
46) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 44) above, wherein said plate cylinder is rotatable to perform main scanning upon said image formation.
47) The computer-to-cylinder type lithographic printing apparatus according to item 46) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction parallel to the axis of said plate cylinder to perform sub-scanning upon said image formation.
48) The computer-to-cylinder type lithographic printing apparatus according to item 46) above, wherein said ejection head comprises a full line head having almost the same length as the width of said plate material.
49) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 48) above, wherein said ink jet drawing device has an ink feed member which feeds said oil-based ink to said ejection head.
50) The computer-to-cylinder type lithographic printing apparatus according to item 49) above, which comprises an ink recovery member which recovers said oil-based ink from said ejection head to circulate said ink.
51) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 50) above, which comprises an ink tank for storing said oil-based ink and an ink-stirring member which stirs the oil-based ink in said ink tank.
52) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 51) above, which comprises an ink tank for storing said oil-based ink and an ink temperature-controlling member which controls the temperature of the oil-based ink in said ink tank.
53) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 52) above, which comprises an ink concentration-controlling member which controls the concentration of said oil-based ink.
54) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 53) above, wherein said ink jet drawing device has an ejection head-retreating/approximating member which approximates said ejection head to said plate cylinder upon said image formation and retreats said ejection head from said plate cylinder except for during image formation.
55) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 54) above, wherein said image-forming unit has an ejection head-cleaning member which cleans said ejection head at least at the completion of plate-making.
56) The computer-to-cylinder type lithographic printing apparatus according to any one of items 32) to 55) above, wherein said lithographic printing unit has a paper dust-removing member which removes paper dusts generated during said lithographic printing.
According to the plate-making apparatus of item 3) above, a filter for ink is inserted between the ink tank and the ejection head, so that foreign matters in the ink can be blocked from flowing into the ejection head and occurrence of unstable ejection state can be prevented.
According to the plate-making apparatus of item 4) above, the filter is disposed immediately before the ejection head, so that a clean ink immediately after the filtering can be fed to the ejection head.
According to the plate-making apparatus of item 5) above, the ink feed device of the ink jet drawing device filters aggregates of ink or foreign matters mingled on the way, such as dust, by a filter and feeds a normal ink to the ejection head, so that ejection in an unstable state due to clogging of the ejection head and troubles due to unstable ejection at the drawing, namely, changes in the dot size or deterioration of the image such as slipping or thinning of the image, can be prevented.
According to the plate-making apparatus of item 6) above, pores different in the shape and the size are present together in the same filter material, so that various foreign matters can be effectively filtered and the ink can be filtered without causing reduction in the filtering rate.
According to the plate-making apparatus of item 7) above, a filter is used as a single layer or a plurality of filters are stacked to form a multilayer structure, so that the filter can be properly used according to the purpose, for example, a single-layer (for example, single plate-type) filter is used in the case where the ink has good quality and the filtering rate is important as in the disposition immediately before the ejection heat, whereas a multilayer-typo filter ensuring high filtering power, scarce clogging and use for a long period of time is disposed in the pump side because a pump pressure or the like is necessary so as not to reduce the filtering rate.
According to the plate-making apparatus of item 8) above, a filter having a coarse pore size is disposed in the ink inflow side to roughly filter the ink and remove main foreign matters, and a dense filter is disposed in the next stage to completely remove foreign matters, so that filtration can be effectively performed over a long period of time without causing reduction in the filtering rate.
According to the plate-making apparatus of item 9) above, the filter can be selected from filters having various forms such as a simple single-plate form, an inline-type tea strainer form capable of taking out and cleaning or exchanging only a filter element on the way, a coming back form of performing circulation filtering through the filter layer divided into a plurality of layers, and a cylinder form including multilayer type and hollow yarn type, by taking account of the quality or volume of ink or conditions such as place for installation or construction or performance of the apparatus.
According to the plate-making apparatus of item 10) above, the construction material of the filter is selected from materials over a wide range by taking account of the use end, such as paper for use having high frequency of exchange or disposal, membrane-type plastic (polymer) material obtained by bundling many hollow plastic yarns to have a cross section of hollow yarn-type filter like a hollow yarn film, metal of wire-mesh type or obtained by stacking and sintering stainless steel metal fiber felts and usable for a long term when washed or cleaned, glass and ceramic.
According to the plate-making apparatus of item 11) above, a hollow yarn-type or multilayer cylinder-type filter for use in a water purifier or the like can be exchanged together with the cartridge housing the filter by a simple and quick operation and in the case of a tea strainer-type (T-type inline) filter, only the element itself can be taken out and returned after cleaning or exchanged while allowing the filter to remain on the line.
According to the ink feed device of the ink jet drawing device in item 12) above, means for cleaning the filter material is provided, so that cleaning and removal can be performed automatically or appropriately by hand at a predetermined timing (for example, every 300 hours of operation).
According to the plate-making apparatus of item 13) above, the accumulation can be removed by means of ultrasonic irradiation or vibration applied to the filter and in addition, by back flow of ink or cleaning solution. In the case of a hollow yarn-type filter, efficient cleaning can be attained by back flow from the water outlet side to the water inlet side.
According to the plate-making apparatus of item 14) above, the filtration is performed by flowing the ink under a pressure resultant from combining gravity filtration using a gravity of the ink itself, pressure filtration using a pump pressure and vacuum filtration using a vacuum pump pressure, so that the filtration can be efficiently performed without causing reduction in the filtering rate (ink flow rate). A pump pressure of the ink feed part, circulation part, tank or the like may also be used as the pressure.
According to the computer-to-cylinder type lithographic printing method of item 30) above, the oil-based ink is used after filtering it, so that foreign matters in the ink flowing to the ejection head can be blocked and the ejection in a stable state can be attained.
According to the computer-to-cylinder type lithographic printing apparatus of item 32), a filter is inserted between the ink tank and the ejection head, so that foreign matters in the ink to the ejection head can be blocked and unstable ejection can be prevented from occurring.
According to the construction in item 33) above, the filter is disposed in particular immediately before the ejection head, so that a clean in immediately after the filtering can be fed to the ejection head.
According to the construction in item 34) above, aggregates of ink and foreign matters such as dust mingled on the way are filtered by a filter and a normal ink is fed to the ejection head, so that ejection in an unstable state due to clogging or the like of the ejection head can be prevented and troubles due to unstable ejection at the drawing, namely, changes in the dot size or deterioration of the image such as slipping or thinning of the image, can be prevented.
According to the construction in item 35) above, pores different in the shape and the size are present together in the same filter material, so that foreign matters having various shapes and sizes can be effectively filtered and the ink can be filtered without causing reduction in the filtering rate.
According to the construction in item 36) above, a filter is used as a single layer, or a plurality of filters are stacked to form a multilayer structure, so that the filter can be properly used according to the purpose, for example, a single-layer (for example, single plate-type) filter is used in the case where the ink has good quality and the filtering rate is important as; in the disposition immediately before the ejection heat, whereas a multilayer-type filter ensuring high filtering power, scarce clogging and use for a long period of time is disposed in the pump side because a pump pressure or the like is necessary so as not to reduce the filtering rate.
According to the construction in item 37) above, a filter having a coarse pore size is disposed in the ink inflow side to roughly filter the ink and remove main foreign matters, and a dense filter is disposed in the next stage to completely remove foreign matters, so that filtration can be effectively performed over a long period of time without causing reduction in the filtering rate.
According to the construction in item 38) above, the filter can be selected from filters having various forms such as a simple single-plate form, an inline-type tea strainer form capable of taking out and cleaning or exchanging only a filter element on the way, a coming back form of performing circulation filtering through the filter layer divided into many layers, and a cylinder form including multilayer type and hollow yarn type, by taking account of the quality or volume of ink or conditions such as place for installation or construction or performance of the apparatus.
According to the construction in item 39) above, the construction material of the filter is selected from materials over a wide range by taking account of the use end, such as paper for use having high frequency of exchange or disposal, membrane-type plastic (polymer) material obtained by bundling many hollow plastic yarns to have a cross section of hollow yarn-type filter like a hollow yarn film, metal of wire-mesh type or obtained by stacking and sintering stainless steel metal fiber felts and usable for a long term when washed or cleaned, glass and ceramic.
According to the construction in item 40) above, a hollow yarn-type or multilayer cylinder-type filter for use in a water purifier or the like can be exchanged together with the cartridge housing the filter by a simple and quick operation and in the case of a tea strainer-type (T-type inline) filter, only the element itself can be taken out and returned after cleaning or exchanged while allowing the filter to remain on the line.
According to the construction in item 41) above, means for cleaning the filter material is provided, so that cleaning and removal can be performed automatically or appropriately by hand at a predetermined timing (for example, every 300 hours of operation).
According to the construction in item 42) above, the accumulation can be removed by means of ultrasonic irradiation or vibration applied to the filter and in addition, by back flow of ink or cleaning solution. In the case of a hollow yarn-type filter, efficient cleaning can be attained by the back flow from the water outlet side to the water inlet side.
According to the construction in item 43) above, the filtration is performed by flowing the ink under a pressure resultant from combining gravity filtration using a gravity of the ink itself, pressure filtration using a pump pressure and vacuum filtration using a vacuum pump pressure, so that the filtration can be efficiently performed without causing reduction in the filtering rate (ink flow rate). A pump pressure of the ink feed part, circulation part, tank or the like may also be used as the pressure.